The present invention relates to a brake booster, and more particularly to a brake booster having an improved reinforcement plate mounted on a brake booster body by which the brake booster and a master cylinder are interconnected.
Brake boosters comprise a body and a casing connected to each other and jointly defining a space which is divided by a diaphragm into a vacuum chamber that is kept under vacuum at all times and an operating-pressure chamber in which atmospheric pressure or vacuum is introduced. The diaphragm is coupled to a power piston connected to a push rod coupled to a brake pedal. When the brake pedal is pushed down, atmospheric pressure is introduced into the operating-pressure chamber to power-assist the movement of the push rod. The motion of the push rod thus assisted under atmospheric pressure is then transmitted to the master cylinder mounted on the body of the brake booster.
The master cylinder is affixed to the brake booster body by bolts fastening an end of the master cylinder to the brake booster body. Direct attachment of the master cylinder to the brake booster body would require the body to be of an increased thickness for sufficient rigidity to support the master cylinder, thus increasing the weight of the brake booster. It has been customary to employ a brake booster body having a reduced thickness and a reinforcement plate for attaching the brake booster body to the master cylinder. More specifically, the reinforcement plate has a doughenut-shaped configuration and is made from a sheet of pressed metal which is attached in intimate contact to the entire inner surface of a central wall portion of the body for distributing stresses over the central inner wall of the body. The master cylinder is mounted on the central outer wall of the brake booster body which is reinforced by the reinforcement plate. When the braking action is applied to the master cylinder, however, high stresses tend to act on an outer peripheral portion of the reinforcement plate, resulting in a greater likelihood for the thin brake booster body to be damaged.